Problems with watching videos on the internet

I have an Apple computer, bought a year ago and a older Dell desktop. Lately I have trouble viewing videos from any sites on the internet. The videos took forever to load or stopped every five minutes on either computer. I am not tech savvy. Any help will be much appreciated.

Check to see if this is consistent across different browsers - i.e. Firefox and Chrome. Usually videos require some plugin (Flash) and you may need to upgrade your plugins. If it plays fine on Chrome, then it's not a plugin issue since Chrome doesn't require you to install these 3rd party plugins. I would also just run a speed test on your internet connectivity to make sure it's fine.